Salinity Management And . - University Of Arizona
Salinity ManagementandDesalination Technologyfor Brackish Water Resourcesin the Arid WestSummary Report of a Workshopheld onAugust 6, 2007Tempe, ArizonaSponsored byArizona Water InstituteU.S. Bureau of ReclamationAugust, 2008
Salinity Management and Desalination Technology forBrackish Water Resources in the Arid WestSummary Report of a Workshopheld onAugust 6, 2007Tempe, ArizonaSponsored byArizona Water InstituteU.S. Bureau of ReclamationAugust, 2008Executive CommitteeSupporting SponsorsWendell Ela*, University of ArizonaChuck Graf, Arizona Water InstituteTom Poulson, U.S. Bureau of ReclamationJim Baygents, University of ArizonaJan Theron, Northern Arizona UniversityPeter Fox, Arizona State UniversityChris Scott, University of ArizonaBrown and CaldwellErrol L. Montgomery & AssociatesDamon S. Williams & AssociatesWorkshop report prepared for publication by*contact and corresponding author. Chemical and Environmental Engineering, University of Arizona,Tucson, AZ 85721. E-mail: wela@engr.arizona.edu
Table of ContentsI. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1II. Source Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3III. RO Pre-Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5IV. Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7V. Post-Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8VI. Local Management and Disposal of Residuals and Concentrate . . . . . . . . . . . . . . .10VII. Regional-scale Concentrate Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12VIII. Summary and Roadmap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14IX. Afterword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17AppendicesAppendix 1- Salinity Workshop Agenda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Appendix 2 - Salinity Workshop Attendees . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Appendix 3 - Annotated Literature Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
I. IntroductionCentral Arizona Project (CAP) water originating in the Colorado River is a primarysource of potable and irrigation water in Arizona. This water source, along with the SaltRiver in central Arizona, brings over 1,000,000 tons of salt each year into central andsouthern Arizona, where it accumulates as the carrier water is used. These salts go primarilyinto the region’s soils and the effluent discharged from wastewater treatment plants. Both ofthese temporary repositories ultimately feed the salt into the groundwater, which is a criticalwater supply for the region.On August 6, 2007, a workshop was convened in Tempe, Arizona to focus on identifyingthe state-of-the art technologies for membrane removal of salt from the region’s watersources while minimizing the attendant water loss and the environmental impact of thetreatment residuals disposal. The workshop focused on identifying and prioritizing the technicalhurdles that must be overcome to improve efficiency and economic viability of treatmentprocesses, and establishing a practical roadmap forward for achieving sustainable, viabledesalination of inland, moderate salinity waters including wastewaters. These workshopobjectives were examined in the narrow context of source water salinities ranging from CAPwater with a total dissolved solids of about 700 mg/l (milligrams per liter) to brackish waterscontaining up to 10,000 mg/l of TDS. Although ocean disposal is a potential option in thedistant future, nearer-term inland disposal options were emphasized for evaluation.The historical, high quality groundwater resources are not sufficient to sustain the current,much less, projected municipal, industrial, and agricultural demands in Arizona. The waterdemand requires full utilization of the State’s allotment of CAP water as well as its availablesurface water sources, including the Salt and Verde River resources. The salinity of CAP andSalt River water, by far the bulk of the surface supply, exceeds the Environmental ProtectionAgency’s Secondary Standard of 500 mg/L for total dissolved solids (TDS). Demand greaterthan these surface and historical groundwater supplies can only be met by wastewaterreclamation and tapping into and treating the region’s brackish water resources. The salinityof both of these latter water resources is greater than current surface water source salinities.The inevitable conclusion is that future water needs will require desalination of a significantportion of the region’s water resources.To illustrate, water demand in the Tucson Active Management Area (TAMA) is estimatedat 400,000 acre-feet per year. However, the rate of natural groundwater replenishment isonly about 60,000 acre-feet per year. The unavoidable shift from ground water to CAPwater as the primary regional water resource will have significant water quality implications.The average TDS concentration in delivered ground water has historically been about 260mg/l. TDS levels at the Tucson terminus of the CAP canal are greater than 700 mg/l andlikely to rise. Full utilization of CAP water allocations will bring 200,000 tons of salt intothe TAMA each year. Without some form of salt management, the majority of this salt willremain, contributing an average of 5 mg/l to the regional aquifer each year.An analogous situation exists in the Phoenix area, where salts are accumulating at a rateof about 1.1 million tons annually. This is not a reversible situation and cannot meet thepublic’s concept of water supply sustainability.The strategy for salt management in central and southern Arizona will almost certainlyconsist of a combination of reverse osmosis (RO) treatment and benign brine disposal.1
Water recovery (the percentage of treated water that is collected as permeate) is of exceptional importance to the community. Although it is difficult to assign a marginal benefit towater supply augmentation through recovery enhancement, Tucson residents have shown awillingness to pay 3 per 1,000 gallons or about 1,000 per acre foot for the highest increment in the tiered rate structure for delivered residential water. Using this value to illustratethe benefits of brine minimization, if the entire TAMA CAP entitlement is RO treated tomanage local salt levels in ground water, each 1% increase in recovery efficiency wouldprovide a benefit to the community of greater than 2M per year. Water recovery from ROtreatment of CAP water is currently limited to about 80%. If methods could be developedto even halve the water loss (increase water recovery from 80 to 90%), it would produce a 20M per year benefit within the TAMA alone. The technology would be equally useful inother Arizona desalination projects.In response to this critical challenge to Arizona, the Arizona Water Institute and theBureau of Reclamation convened a technical workshop entitled “Improving SalinityManagement and Desalination Technology for Brackish Water Resources in the Arid West”on August 6, 2007, in Tempe, Arizona, at the Tempe Mission Palms Hotel. Workshopinvitees from governmental agencies, water utilities, consulting firms, academia, and otherstakeholder groups were selected for their technical expertise and involvement in the subject.(A workshop agenda and a list of participants are included as appendices to this report.)The workshop was specifically structured to encourage discussion between representativesof the key stakeholder groups on ways to address the inland desalination and concentratemanagement challenges and on identification of the critical research hurdles that must beovercome for implementation of viable strategies.The closest to a unanimous conclusion reached by the participants in the Workshop wasthat ‘there is no silver bullet’. Although there is no single, one-size-fits-all technologicalsolution to the inland salinity management problem, a range of options is available that canbe applied in various combinations to meet case-specific conditions. A sustainable, economically viable and technically feasible solution will consist of a number of different mutuallyreinforcing technologies and efforts, the particular nature of which will vary according tothe size, location and circumstances of the water supplier and other factors. Within theoverall Arizona region the solution will include technologies and strategies for:1) minimization of the transport of salt into the region (e.g., by minimizing the needand motivation to use home water softeners),2) pre-treatment of RO feed water to increase water recovery and membrane performance,3) improving the performance of membranes and the membrane separation process itself,4) post-RO treatment of the concentrate stream to increase the recovered water, extracteconomically viable concentrate components, and reduce the concentrate volume, and5) management and disposal of the remaining concentrate and other residuals.The following five sections of the report address discussions that occurred regardingeach of these five components of a holistic approach to salinity management. Obviously, allissues raised and points made in the workshop do not neatly fall into only one of the areasenumerated. Consequently, a best fit for each topic was attempted, but some topics areaddressed in more than one category with some overlap.2
II. Source ControlShort of desalting surface water before it enters the region, such as by implementing ROtreatment at the mouth of the CAP canal, a significant mass of salt will enter the regionalong with the surface water supplying Arizona’s water needs. However, the water conveyedby the CAP canal is not the only source of imported salt. In the Phoenix region a significantmass of salt is contributed by the Salt and, to a lesser extent, the Verde River. In addition, alarge and rapidly increasing mass of salt is introduced because of the use of ion exchangehome water softening devices. Although the devices remove multivalent cations, the totalsalinity (in terms of equivalents per volume) of the product water is not decreased and, inaddition, a highly saline brine is generated. Because this salt addition occurs after treatmentby centralized water treatment facilities and at the point of use of the drinking water, theextra salt load is conveyed to the sewer and seen as a higher wastewater salinity than standardcalculations predict. This load has potential negative impacts on the riparian ecosystemsupported by the wastewater discharges, on the uses of the reclaimed water, on the WWTPprocesses themselves, and on the overall rate of salt accumulation in the region.Proliferation of home and small commercial water softener use is, at least partially,motivated by a desire to avoid premature failure or frequent maintenance of water-relatedhome appliances, such as water heaters, irons, swamp coolers and coffee makers, due toprecipitative scaling by hardness-causing cations. As the salinity and hardness of drinkingwater supplies increase, it is expected that watersoftener use will also increase. Two approacheswere discussed to counteract this trend: implement system-wide water softening to eliminate theneed for individual point-of-use water softeners ordiscourage their use through disincentives or othermeasures. These approaches are not mutuallyexclusive and could be implemented to somedegree in tandem.The former approach is typically accomplishedby centralized lime softening (or variations of thisprocess), although nanofiltration or reverseosmosis processes may be used if other waterquality considerations suggest they may provideadditional benefits. Alternatively, implementationof centralized capture and regeneration of spention exchange softening resins (for instance via aprovider switch-out program) would allowimproved residual management and enhancedwater recovery by incorporation of processesthat are not amenable to point-of-use homesoftening (e.g., brine recycle, rinse/backwashrecovery, precipitative softening of brines).As to the latter approach, workshop participantssuggested several means of discouraging home3
water softener use. These include a tax/surcharge on softener salt, a surcharge for softenerinstallation in new homes, or restrictions on the use of self regenerating softeners. This latterstrategy would force regeneration of spent softener resins at centralized facilities where thehigh salinity regenerant residual could be more easily treated or managed to minimizenegative impacts. Although the practicality of implementation of these (dis)incentives towater softener use was not discussed, there was considerable interest voiced in furtherinvestigating such means to discourage use.A final potential approach to decreasing the salt impact of home water softeners is theuse of capacitive deionization devices. This technology is still not fully developed and commercialized, but could potentially compete with ion exchange for home softening purposes.The advantage of capacitive deionization is that it does not increase the overall salt loadsince softening is driven by an input of electrical energy rather than monovalent ions. Theprocess produces an ion-reduced finished water and a brine concentrate, but with no netincrease in overall ion content. This technology (at least, at its current stage of refinement)is not economically competitive with current technologies due to the high cost of membranematerial (normally Aerogel) and the low ion site capacity of the membranes.4
III. RO Pre-TreatmentReverse osmosis pre-treatment generally includes a variety of technologies and techniques to decrease both fouling and scaling of the membranes. Fouling occurs due to thebuild-up of particles (organic and inorganic, colloidal and particulate) that are in the feedwater and deposit on the membrane surface. Fouling is usually most pronounced on themembranes in the front-end stages of an RO array. In contrast, scaling occurs due to theprecipitation of supersaturated salts on the membrane surface. The degree of precipitationincreases as the concentrate stream progressively moves through the sequential RO elementsand increases in salinity. Scaling is a problem typically in the back-end stages of an ROarray where the reject stream’s salt concentration is near its maximum.Conventional water treatmentprocesses (e.g., sedimentation,coagulation/flocculation, filtration)as well as other processes, suchas slow sand filtration, microand ultrafiltration, and activatedcarbon filtration, can be effectiveat removing fouling componentsof the raw water. Micro- andultrafiltration are becomingmore widely used to removefoulants ahead of RO becausethey have a relatively smallinstallation footprint, are reliableand well field tested, and theirprice is becoming competitivewith alternative processes. ForMembrane scaling of supersaturated salts (BaSO4)many Arizona utilities, availabilityof land is not a primary constraint, so slow sand filtration (SSF) may be an option to lessenfeed water fouling indices. The Water Quality Improvement Center at Yuma, initiated bythe US Bureau of Reclamation, the National Water Research Institute, the U.S. Army andother research institutions, has studied pre-treatment by slow sand filtration and recommendsit for consideration, particularly for rural installations. There is the possibility of improvingSSF removal of colloidal solids and dissolved organics by developing better engineered filtermedia and by sand amendment with such things as granular activated carbon and ironparticles. Improved engineering to control schmutzedecke development and various periodiccleaning methods should also be pursued to optimize SSF performance.Pre-treatment technologies and techniques to control or delay the onset of scalingreceived considerable discussion. These RO pre-treatment processes can be classified intotwo groups based on their mode of action in dealing with the limiting (least soluble) salts,which are responsible for initiating scaling on the final stage membranes. One group ofprocesses acts by removing the limiting salts prior to membrane application. The secondgroup includes processes that increase the solubility of these sparingly soluble salts. In eithercase, the outcome is increased water recovery prior to the onset of scaling.5
The salts most commonly responsible for scaling are calcium carbonate (CaCO3), bariumsulfate (BaSO4), silica (SiO2), calcium sulfate (CaSO4), calcium fluoride (CaF2), strontiumsulfate (SrSO4) and magnesium hydroxide (Mg(OH)2). The processes discussed by workshop participants to remove these components from the feedwater prior to RO were 1) ionexchange and 2) precipitative processes, including softening. As to the first, cationic ionexchange resins are more commonly used than anionic resins, primarily because neithercarbonate, fluoride, nor silicate are readily removed by anion exchange, whereas calcium,magnesium, strontium and barium have relatively high affinities for common cationic resins.However as discussed earlier, ion exchange requires addition of salt (typically NaCl) tomaintain the regenerant brine, so there is a net increase in salt in the system (although it isconfined to the waste brine stream).More commonly, precipitative removal of the divalent cations is used to control scalingsalts in central treatment facilities. Traditionally, this is done by either addition of caustic(NaOH), lime (CaO), or lime and soda ash (Na2CO3); depending on the raw water composition and the cations targeted for removal. A number of workshop participants commentedon the need to improve the selectivity and efficiency of precipitative processes by suchthings as polymer addition (to increase floc settling rates and sludge dewatering), specificion addition (to target early precipitation of certain cations) and designer particle addition(to provide preferential nucleation sites and increase settling rates). There was also discussion ofrecovery of reusable and potentially saleable products from the sludge residual (althoughthis discussion focused primarily on selective precipitation as a post-RO treatment processand will be covered in that section of this report).The alternative to removing the limiting salts prior to RO is to manipulate the feedwatercomposition to increase the solubility of the limiting salts. Sulfuric acid is often added tolower the feed pH, which decreases both the carbonate concentration by converting bicarbonate to volatile carbon dioxide and the hydroxide concentration. However, if sulfuricacid addition is not prescribed because sulfate salts are limiting (e.g., BaSO4), hydrochloricacid is often used. A disinfectant must also be added to feedwater to prevent microbialgrowth in the RO system. Polyamide (PA) membranes have largely replaced celluloseacetate (CA) membranes because of their greater chemical and physical stability, greaterwater fluxes and salt rejections and resistance to bacterial degradation. However PAmembranes are intolerant of free chlorine, so disinfection in these systems is typically bycombined chlorine (chloramines). Considerable work has been performed to improve theoxidant tolerance of polyamide membranes in particular, and other membrane materials ingeneral. There are a wide variety of proprietary antiscalant additives, which allow thesupersaturation (increase in solubility) of the limiting salts to varying degrees. Inorganicphosphate additives have been largely replaced by organic polymer additives. These additives allow supersaturation factors of from 2 to several orders of magnitude depending onthe type of limitin
Central Arizona Project (CAP) water originating in the Colorado River is a primary source of potable and irrigation water in Arizona. This water source, along with the Salt River in central Arizona, brings over 1,000,000 tons of salt each year into central and southern Arizona, where it accumulates as the c
salinity of water by hydrometer. Similarly salty water refracts more than freshwater and this property is the reason for measuring salinity of water by refract meter. As the property of variation of microwave emissivity with temperature and salinity of sea surface, salinity sensor is mounted on NASA’s Aquarius Instrument satellite (June
Modelig Low Salinity Waterflood and Low Salinity Surfactant flooding". But other than that there are no specific geologic structures other than a difference in absolute permeability between the regions. The horizontal grid-sensitivity of the system and how it affects fluid flow, dispersion, and production will be emphasized in this study.
The aim of the present work was to study the effect of salinity and water stress on plant performance in different giant reed clones. To this end, two separate experiments were carried out. Firstly, a study with both stresses was performed (experiment 1). This experiment aimed to determine the effects of salinity and water stress on
dissolved in root zone soil moisture to adversely a ect the plant growth (Rengasamy, Chittleborough, & . of soil salinity levels and mapping of salinity a ected areas (Katsaros, Vachon, Liu, & Black, 2002). . 2005). High resolution optical datasets are mostly available on commercial and paid basis and almost all currently active SAR .
A method and apparatus are described for disposing of salt byproduct from a zero liquid operation, such as a zero liquid discharge desalination plant. The present method and apparatus concern a power generation plant, comprising a salinity gradient power unit (SGPU) comprising a high salinity feed, a low salinity feed, and a mixed water output.
Troubleshooting - Front Board Disconnect the flow salinity temp sensor from the front board. Press and hold the test buttons marked salinity and R-temp. While still pressing the test buttons press the ‘Salinity’ key (‘C’) on the front cover of the unit. The LCD should read 2.8 gpl*.
Describe the value of ocean salinity in refining our quantitative understanding of the global water cycle; in governing the global ocean . advance of and during the Aquarius/SAC-D mission to improve the measurement, analysis, and utilization of salinity information for the purposes stated above.
The Brazos River Authority (BRA) and Southern Trinity Groundwater Conservation District (GCD) are aware of the variability of salinity in the Brazos River Alluvium aquifer, and are interested in a study to identify the sources of salinity.
